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A computer model called ALMANAC promises to provide answers about a key issue facing agriculture today: The management of crops such as corn and switchgrass for bioenergy production.

Agricultural Research Service (ARS) Agronomist Jim R. Kiniry at the Grassland Soil and Water Research Laboratory in Temple, Tex., and his colleagues originally developed ALMANAC as a crop-management tool, then updated it as a pasture management tool. Now it's being used to evaluate biofuel crops.

After its development in Texas, the model was tested in northern states in 2005. It accurately predicted switchgrass yields in 10 fields in North Dakota, South Dakota and Nebraska. The model's predicted yields each year were within 1 to 10 percent of actual yields over all fields.

In another study with northern and southern populations of upland and lowland switchgrass, the model showed realistic simulated yields in Wisconsin, Kansas and Oklahoma. In these two studies, the measured yields ranged up to 6.7 tons per acre.

Kiniry and colleagues simulated growing corn and four varieties of switchgrass in the southern and northern Great Plains and the Corn Belt. ALMANAC projected that switchgrass would use only half as much water per pound of material produced as corn grown for grain.

ALMANAC's estimated switchgrass water-use advantage was reduced when model inputs specified that entire corn plants were to be used for ethanol production rather than just the grain. In this way, ALMANAC helps farmers determine the most appropriate crop for their fields under current market and environmental conditions.

By predicting outcomes on arid rangeland, marginal lands and more fertile lands like the Corn Belt, ALMANAC can help farmers alleviate concerns about shifting acres from food to fuel.

Kiniry’s team also used the model to predict the benefits of anticipated breeding improvements in switchgrass. They found new varieties might increase yields 2 percent to 16 percent and water use efficiency by 2 percent to 7 percent.